Energy Performance of Buildings: A Comparison of Standard Assessment Methods - Nearly Zero Energy Building Refurbishment - page 192

Table 7 Influence of heat generator subsystem losses
Case study Calculation method EP H EP gl Energy class

A5.a Table 23 397.54 419.81 G

A5.b B1 316.87 336.06 G

A5.c B2 420.49 437.00 G

B4.a Table 23 177.89 205.83 G

B4.b B1 177.76 206.46 G

B4.c B2 195.5 223.93 G

Table 8 shows the results applying the two different methodologies to case A:
the gap in terms of performance indicator for heating among the results applying
the two procedures is about 3 %.
Table 8 shows also the results obtained by the application of the two different
methodologies to case B, and it is apparent that, in this case, the gap in terms of
performance indicator is negligible.

7.7 The Influence of Emission and Control Subsystem
Losses

Another possibility of intervention is the improvement of the control subsystem, as
an alternative or in addition to heat generator substitution. For case A, the
installation of a thermostat with 99 % efficiency is provided, instead of case B,
which is characterized by the use of thermostatic radiator valves with 98 %
efficiency.
Table 9 highlights how an efficient control system can influence building per-
formances. Moreover, it is apparent that also in this case the methodology adopted
for the generation losses calculation significantly affects the global efficiency of
the building g gl with a gap of about 23 % between case A7.d and A7.c, even if the
class is always G.
Comparing the results for case A7.a with the base case performances (A0.a), it
should be noted that the intervention in the control system can lead to a reduction
in the EP gl index which accounts for about 10 %. Regardless of the adopted
assessment procedure for the generation losses, considering cases A5 (a, b, c) and
A7 (a, b, c), the boiler substitution associated with the improvement in system
control reduces the energy needs about 10 %. It is so significant to notice that
comparing cases A7.d and A7.c (or A5.b and A5.c), which are characterized by the
same level of intervention, but with two different calculation methods for gener-
ation losses, the percentage gap in terms of global energy performance accounts
for 22 %. Consequently, choosing accurately the calculation method of generation
losses, the building could reach a more efficient energy class than the reachable
one with the substitution of the control system. Analogue considerations could be
done for case B.